It is not necessary for the First block of BCC to be mined in order to sell your BTC. You can sell BTC at anytime... if you have it on an exchange like Poloniex. However, it is still unclear whether or not you need to hold your BTC on an exchange that will issue BCC in order to get it. See some of the comments above... seems like you don't need to wait... but your call.
RE: Are you ready for the Bitcoin Fork? Whats my trading plan for THE FORK?